Question details

Transaction overrun-Property Transfer

Hi,

I am using property transfer to write to an OPC Server.I tried to takeout the overrun happening.Total number of signals getting transferred is 230.First I limit the number of signals in each property transfer aspect to 20. Then set different update rate like 1000ms,1200,1400 etc...I am getting overrun

Second set the update rate of all signals as 2500..then also go the over run

I know that limitation of property transfer is 100signals/second.Also property transfer updating on change.Does this means that if any one signal value changed it will transfer all the signals in that aspect ?

Reduce the number of property transfer aspect to 6(each having nearly 40 signals)..Configured different update rate like 1000,1200,1400 etc..got overrun

Configured update rate of all aspect to 2500...got overrun

Also found that if I am using the functinality(Transfer all property every) from 800xA 5.1RevD then I can see more overrun messages.As of now I disabled that option.

Anybody can suggest how to transfer without overrun ?

Also I know the limitation of signals can transfer via property transfer is 1000. What will happen if transferring 2000 signals via property transfer ? 800xA system will behave strangly ?

What will happen if I leave the messages whether property transfer will hang after a period ?

Answers

0

Hi!

What Connectivity do you use in your system (AC800M etc)? Performance differs between different OPC servers.

For instance, from the manual; "The AC800M OPC can not handle more than 50 simultaneous writes per OPC-group". Try to increase cycle time to 6000ms and split cycle times between the groups to an odd number like 5999ms, 6000ms, 6001ms etc...

There are a number of disadvantages with PT and performance varies between OPC-servers and their respective controller/PLC-communication bandwith. I've only used PT with small amount of data, if you need performance I would consider writing (Controller)PLC to PLC communication bypassing 800xA.

Overrun = an even newer update from source OPC server is received before the previous write has completed by the destination OPC server.

False errors can be output by Property Transfer service provider in Standby state, toggle the service to recover from that bug.

Increase source rate until destination has time to complete the writing.

Afaik, only changed properties will transfer (unless Transfer All Every... function is enabled)

The Property Transfer service is probably not the bottleneck - the destination is often the limiting factor.

During failover to redundant service provider (if configured) ALL items will be written at once - you may perhaps ignore warnings seen at failover.

One enhancement that we desire would be to be able to queue writes in larger bulks. Current implementation results in one tiny AsyncWrite() per changed item in the source end (I assume OnDataChange with multiple items are queued together in the write though). But if source is sending updates with just one item per update, there will be a lot of small writes output to the destination. Would probably be better if the Property Transfer allowed a "Group Writes" option where a deadband/timeout value could be set, eg 1000 ms; that would probably reduce number of distinct write ops a lot gaining speed in a destination server having large overhead in small writes.